This invention relates to an improved method of joining together fabric or other sheet material, particularly floor covering material such as carpets, and apparatus therefor.
Sheet materials, such as carpets, are commonly joined edge to edge by sewing the adjacent edges together. In some instances, the carpet is "made", i.e., the edges are joined together, prior to the carpet being delivered to the site of its installation, although machines are now available for sewing the carpet in situ. However, such sewing is time consuming and therefore relatively costly, and many types of carpet or other sheet material are unsuitable for joining by sewing.
It is well known to join adjacent edges of sheet material, such as carpets, by adhesive means. More recently, adhesive bonding of carpet edges has become standard practice with the advent of both pressure sensitive adhesives applied to a carpet joining tape and heat activated adhesives on a carpet joining tape or backing.
Australian Pat. No. 464,878 describes a carpet bonding tape which consists of a layer of heat insulating materials such as paper, a layer of metal foil and an upper layer of a ribbon of heat softenable adhesive composition, the nature and thickness of the ribbon of heat softenable adhesive composition being such that an adhesive bond is formed with the underside of a carpet material when the tape is used in an operation in which the carpet material is pressed onto the heat softened adhesive layer. A woven textile material may also be embedded in the ribbon of adhesive material to reinforce the tape.
Many other forms of tape are known which comprise a layer of heat softenable adhesive composition laminated to a paper backing, with a textile reinforcement either secured to the backing or located within the layer of heat softenable adhesive.
Such previously known tapes are generally used in conjunction with a heating iron which applies heat to the tape, either through the backing or through the carpet, to thereby melt the adhesive which then engages with the carpet backing to thereby bond the carpet to the tape, and particularly to the reinforcing textile normally included within the tape.
While such tape and joining methods are relatively successful, difficulty has been found in applying the correct amount of heat and for the required period of time to assure that the adhesive correctly melts and bonds the carpet backing to the tape. Further, the application of too much heat to the surface of the carpet may result in damage being caused to the carpet fibers, particularly if the carpet is formed of a synthetic plastic material such as polypropylene, nylon or the like. Still further, once the carpet is bonded to the tape, any corrections in the pattern matching of the carpet or gaps which appear at the joined seam are difficult, if not impossible, to carry out.
Australian Pat. No. 453,405 describes an improved method of joining sheet material, such as carpet, with heat activated thermoplastic adhesives, wherein a tape comprising a strip of metal foil bearing a heat softenable adherent layer is used, the heat required to activate the thermoplastic adhesive composition being obtained by passing an electric current through the metal foil to thereby cause melting of the adhesive composition and bonding of the adjacent abutting edges of the sheet material.
However, the apparatus required to provide the necessary electric current to the metal foil requires constant supervision by the operator to prevent the foil overheating and thus damaging the sheet material and to assure that the adhesive is melted throughout the length of the tape so that the sheet material edges may be properly joined. Further, once the adhesive has been melted and the electric current removed, the carpet is bonded to the tape, thus preventing corrections for pattern matching or closing gaps which may occur in the seam formed by the joined abutting edges.
It is therefore an object of the present invention to provide an improved method and apparatus for joining sheet material in edge abutting relation whereby the join can be made relatively quickly and simply and yet any corrections which may be necessary can be easily carried out without disturbing correctly abutted edge portions.
It is also an object of the present invention to provide apparatus for use in controlling the heat applied to a heat softenable adhesive so as to enable abutting edge portions of carpet to be quickly and simply joined together.